[PATCH] ASoC: SOF: imx8: add core shutdown operation for imx8/imx8x

[Laurentiu Mihalcea <laurentiumihalcea111@gmail.com>]

From: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>

Currently, the DSP core from i.MX8QM/i.MX8QXP is able to operate while the
firmware image is being loaded. Because of this, the DSP may change the
content of the firmware data just after it was loaded, thus leading to the
data having unexpected values when the DSP is reset (via run()).

Fix this by implementing the core_shutdown() operation that will put the
DSP in stall during suspend(). The stall will be removed during the run()
opertion, thus guaranteeing that the DSP core will not be able to run
while the firmware image is being loaded.

Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>
---
 sound/soc/sof/imx/imx8.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/sound/soc/sof/imx/imx8.c b/sound/soc/sof/imx/imx8.c
index a40a8047873e..b73dd91bd529 100644
--- a/sound/soc/sof/imx/imx8.c
+++ b/sound/soc/sof/imx/imx8.c
@@ -40,6 +40,19 @@ struct imx8m_chip_data {
 	struct reset_control *run_stall;
 };
 
+static int imx8_shutdown(struct snd_sof_dev *sdev)
+{
+	/*
+	 * Force the DSP to stall. After the firmware image is loaded,
+	 * the stall will be removed during run() by a matching
+	 * imx_sc_pm_cpu_start() call.
+	 */
+	imx_sc_pm_cpu_start(get_chip_pdata(sdev), IMX_SC_R_DSP, false,
+			    RESET_VECTOR_VADDR);
+
+	return 0;
+}
+
 /*
  * DSP control.
  */
@@ -281,11 +294,13 @@ static int imx8_ops_init(struct snd_sof_dev *sdev)
 static const struct imx_chip_ops imx8_chip_ops = {
 	.probe = imx8_probe,
 	.core_kick = imx8_run,
+	.core_shutdown = imx8_shutdown,
 };
 
 static const struct imx_chip_ops imx8x_chip_ops = {
 	.probe = imx8_probe,
 	.core_kick = imx8x_run,
+	.core_shutdown = imx8_shutdown,
 };
 
 static const struct imx_chip_ops imx8m_chip_ops = {
-- 
2.34.1